Machines including, for example, wheeled loaders, tracked loaders, track type tractors, and other types of heavy machinery, may be used for a variety of tasks. These machines may include a power source, such as an engine, that provides the torque to torque consuming devices in the machine, so that the machine can perform those tasks. A machine may include a control system to apportion the torque from the power source among the torque consuming devices. The control system may obtain a variety of machine inputs, and based on those inputs, may determine how much torque to apportion to each torque consuming device.
One torque consuming device a machine may include is a hydrostatic transmission, which may include a fluid motor and a pump, that may consume torque from the power source while performing various operations. The control system of the machine may apportion torque to the hydrostatic transmission based on a speed ratio, that is, a ratio of motor speed to pump speed. For example, the control system may determine pump and motor displacements to try and achieve a desired speed ratio. However, during operation, the machine may encounter a load where limitations associated with the machine's power source may prevent the desired speed ratio from being achieved. To handle such situations, the control system may include an underspeed control to reduce the desired speed ratio. In one form of underspeed control, the speed, acceleration, and/or deceleration of the power source is sensed, and is used to reduce the desired speed ratio. Such sensed data, however, may be a lagging indicator that may delay reaction of the underspeed control until machine performance has already been negatively affected.
The disclosed machine control system and method is directed at overcoming one or more of the problems set forth above, as well as other problems known in the art.